1. Field of the Invention
The present invention concerns a method of detecting a visibility interference phenomenon for a motor vehicle, and a detection device for implementing the method.
It finds a particular application in the field of motor vehicles.
2. Description of the Related Art
In the case of an application to a motor vehicle, a method of detecting a visibility interference phenomenon, such as fog, known from the prior art, uses a video image for detecting fog at night when the headlights are in the main-beam position so as to measure the visibility distance.
For this purpose, it uses the light halo forming an ellipse that is generated by the diffusion of the light through the layer of fog. The fog is detected according to the parameters of this ellipse and the calculation of an approximation error between the ellipse and the halo.
One method is known from the article by Nicolas Hautière et al: “Automatic fog detection and estimation of visibility distance through use of an onboard camera”, which appeared in the journal “Machine Vision and Application”, Springer-Verlag, BE, vol 17, No 1, of 1 Apr. 2006. This article discloses the use of an onboard camera to automatically detect fog and visibility distance.
One problem with this prior art is that it does not make it possible to detect fog of medium or low density, since such fog does not generate a sufficiently visible halo to form an ellipse when it is illuminated by the headlights, the said halo consequently not being able to be used for detection of the fog.